Mechanical oscillator



April 28, 1959 c. E. SPEAR 2,833,867

MECHANICAL OSCILLATOR Filed July 12, 1957 2 Sheets-Sheet 1 I 78 tlllll/l/l/l/FIll/l/l/l/l/J F/G. 2. F/G. 3.

VENTOR.

IN CHARLES E. SPEAR WJW ATTORNEYS April 1959 c. E. SPEAR 2,883,867

MECHANICAL OSCILLATOR Filed July 12, 1957 2 Sheets-Sheet 2 IN VEN TOR. CHARLES E. SPEAR ATTORNEYS United States Patent 2,883,867 MECHANICAL GSCILLATOR Charles E. Spear, acrament0, Calif. Application July 12, 1957, Serial No. 671,533 6 Claims. (Cl. 74-30) The invention relates to mechanisms for inducing vibration in structures associated therewith and, more particularly, to mechanical devices capable of producing an oscillating motion of predetermined frequency.

Numerous vibration-inducing devices have in the past been made and used in a variety of fields. Exemplary of such devices are eccentrically loaded and reciprocating weight mechanisms utilized in the mixing and ore concentrating industries. While the commonly used vibrators serve in a reasonably satisfactory manner in such environment, their cost and complexity has militated against their use in connection with smaller structures in which weight and cost, capital as well as upkeep, is an important factor.

It is therefore an object of the invention to provide an oscillator which is relatively economical to make and which requires but a minimum of maintenance.

It is another object of the invention to provide an oscillator which can be used in the vicinity even of children without fear of harm from the oscillating parts.

It is yet another object of the invention to provide an oscillator which can be used, for example, on a childs cradle or crib so as to induce a rocking motion therein conducive to sleep.

It is a further object of the invention to provide an oscillator whose periodicity or frequency can readily be changed so as to induce in the associated structure an oscillation corresponding to its natural frequency, if desired.

it is still a further object of the invention to provide an oscillator which is susceptible of use in a wide variety of environments.

It is another object of the invention to provide a generally improved mechanical oscillator.

Other objects, together with the foregoing, are attained in the embodiment described in the following desc tion and shown in the accompanying drawings in which:

Figure 1 is a perspective showing the oscillator mounted on a resiliently supported childs crib;

Figure 2 is a median vertical section, the plane of section being indicated by the line 2-2 in Figure 3;

Figure 3 is a transverse section, the plane of section being indicated by the line 33 in Figure 2;

Figure 4 is an elevation of the shaft track portion of the oscillator as viewed from the plane indicated by the line l -4 in Figure 2, but with the motor shaft displaced from the shaft track;

Figure 5 is a view comparable to Figure 4 but with the motor shaft in engagement with the top surface of the shaft track flap and moving in a right-hand direction; and

Figure 6 is a view comparable to Figure 5 but with the shaft moving in a left-hand direction and being in engagement with the bottom surface of the flap.

While the oscillator of the invention is susceptible of numerous physical embodiments depending on the environment and requirements of use, considerable numbers of the herein shown and described embodiments have been made and used and have performed in an eminently satisfactory manner.

The oscillator, generally designated by the numeral 11, includes a box-like housing 12. having an inner wall 13, an outer wall 14, a pair of opposite side walls 15, and a bottom 16 as well as a top wall 17. The top wall 17 includes an inward extension 18 downturned to form a flange 19, the housing 12 being clamped to the footboard 21 of the childs crib 22, for example. Clamping is efice fected by appropriately taking up on the handles 23 of a pair of threaded stems 24, shoes 26 on the stem ends serving to clamp the footboard portion interposed between the shoes 26 and the flange 19.

It is to be understood that the use of the oscillator with the childs crib is only exemplary and that comparable results are also obtainable with mining or other machinery, particularly of the lighter variety, requiring similar vibratory or oscillatory conditions and motions. However, the embodiment depicted has been used many times on a childs crib and has served time and again both to pacify a child in the crib and to lull it to sleep.

To realize optimum effectiveness the crib 22 is mounted on a plurality of resilient members 31, such as helical springs, atlixed to the bottom of each of the cribs legs 32.

An appropriate pair of electrical conductors 36 connects the oscillator to an electrical outlet by means of a plug 37, while a line switch 38 mounted either on the footboard, as shown, or adjacent the parents bed serves conveniently to control the on and off condition of the oscillator as desired.

The oscillating mechanism, generally characterized by the numeral 41, includes an axle 42 appropriately mounted at one end in a bushing on the inner wall 13 and at the other end in an aperture in a transverse strap 44 extending between the opposite side walls 15, the strap 44 being somewhat flexible to permit a slight outward bowing for insertion of said other end 45 of said axle through the aperture of the strap 44 during assembly. Preferably the interior of the axle is hollowed out to serve as a conduit for the electrical conductors 36 which enters the housing through a grommeted opening 47 and pass interiorly into the axle through an aperture 48, the conductors emerging from the axle through an opening 49 where the conductors diverge and lead to the appropriate terminals of a small conventional electric motor 51 provided with the customary field windings 52 and rotatable armature 53, the armature shaft 54 being extended outwardly to form a traction portion, designated by the numeral 55.

The motor 51 is itself mounted adjacent the margin of a disc 61, or plate, conveniently circular in outline, as by a suitable fastening 62. The disc 61, in turn, is rotatably mounted on the axle 42 in coaxial fashion. Additional. motor support is provided by a truncated triangular plate 63 rotatably mounted on and depending from the axle 42, the plate 63 being secured to the motor as by fastenings 64.

it can therefore be seen that the disc 61, the plate 63 and the depending motor are, within limits, free to swing back and forth in a plane transverse to the axis of the axle 42, the axis also being the center of rotation or oscillation of the mass. The center of gravity of the mass, however, is at a location removed from and in a downward direction from the center of rotation. Consequently, as the center of mass is moved first to one side and then to the other side of dead center, measured from a vertical median plane through the axis of the axle 42, unbalance occurs, the unbalanced moment being transmitted through the axle to the housing and thus to the resiliently supported crib structure, inducing the crib to vibrate, or oscillate, about the longitudinal crib axis. When the frequency of the oscillator is made to match the natural frequency of oscillation of the crib a sub I stantial amplitude of crib movement occurs.

Novel mechanism is provided both for eifecting oscillation of the disc and motor elements and for progressively changing at will the frequency of oscillation of such elements to any predetermined value.

Oscillation or back and forth rocking of the disc'motor mass is effected by traction engagement between the traction portion 55 of the rotating motor shaft 54 and a flexible, resilient inclined flap 71, or strip, of material, such as rubber, mounted on a bracket 72 depending from the axle 42, the bracket 72 being spaced from the oscillating mounting 73 of the plate 63 as by a felt washer 74. As shown most clearly in Figure 2, the lower end of the bracket 72 is bent into a reversed C-shape, in section, there being an upper wall 76, a lower wall 77 and an outer wall 78. A convenient way of mounting the flap 71 on the walls of the C-bracket is to slit the fiap over the central portion of its transverse width and insert the C-bracket through the slit, thence sliding the flap along the lower wall 77 and up the outer wall 78 until the flap assumes the inclined attitude shown in Figures 3 through 6.

Preferably the parallel track walls 76 and 77 are at least somewhat arcuate in contour and thus form between them an arcuate slot 81, or channel, through which the traction portion 55 of the motor shaft swings.

As appears most clearly in Figures 4 through 6, the resilient flap 71 is not only inclined but it traverses and thus angularly blocks the entire cross-section of the arcuate channel. Consequently, as the motor shaft, rotating in the direction indicated by the arrow 82, moves toward the flap in the direction of the arrow 83, engagement shortly occurs between the shaft and the upper surface 86 of the flap 71. The engagement between the rotating shaft and the resilient flap results in a tractive effort being exerted by the shaft on the flap. This tractive effort, in turn, causes the shaft to roll or crawl up the path offered by the upper surface 86 of the flap. Actually, the flap is progressively depressed, as appears in Figure 5, as the shaft proceeds, the inclined flap continually olfering a frictional path which the shaft can engage. Obviously, as the rotating shaft moves toward the right through the channel 81, the attendant motor and disc are likewise swung, an imbalance being produced as the center of mass swings past the plane of dead center 87.

Inertia carries the shaft 55 beyond the right hand end 88 of the flap 71 as shown by the arrow 89 in Figure 5. Immediately upon this occurrence, the flap, owing to its resilience, resumes its initial angularly inclined attitude appearing in Figure 4. Thereupon, inertia having spent its force, gravity swings the motor and the shaft 55 in a left hand direction, as shown by the arrow 91 in Figure 6, the shaft thence coming into engagement with the lower surface 92 of the flap 71 and rolling across the lower surface by virtue of the tractive effort exerted by the shaft. Upon reaching and passing beyond the left hand end 93 of the fiap, the flap again assumes the initial or normal position shown in Figure 4 and the cycle of oscillation again commences.

While frequency of oscillation can be varied in a number of ways, including radial displacement of the center of mass, it has been found that a highly convenient, progressive and nice control of the period is obtained by exerting a controlled tension on the disc 61 as by a spring 95 aifixed at its lower end to the bracket wall 76 and connected at its upper end to a cord 96, or small cable, reaved about a drum 97 suitably mounted on the disc substantially on the median vertical plane through the center of mass, the tension on the spring being adjustable by rotation of a knob 98 projecting exteriorly of the housing through an arcuate slot 99 in the housing, as shown in Figure 1. The knob 93, in other words, can conveniently be rotated and the spring tension adjusted from outside the housing. As can most clearly be seen in Fimire 3, as the disc oscillates, the spring rocks back and forth about its lower end as a center, somewhat in the fashion of a toggle mechanism. Thus, if the disc is swung by the motion of the shaft 55 in the counterclockwise direction indicated by the arrows 101 so that the spring is offset toward the left, the tendency of the spring is to pull the disc in a counter-clockwise direction and thus to increase the extent of disc movement. Consequently, increasing the spring tension tends to increase the amplitude and period of swing of the disc and thus to reduce the frequency of oscillation. A comparable result is effected when the disc swings in the clockwise direction shown by the arrows 102, the spring again exerting a greater or less effort on the disc depending on its tension, the spring at all times, however, tending to increase the amplitude of the swing on either side of dead center.

While spring tension could also be varied by vertical motion of a machine screw mounted vertically on the top 17 and projecting downwardly to connect with the spring, the shown and described device is highly satisfactory and the oscillating knob 98 could be coated with a material capable of glowing in the dark, thus giving notice to the parents that the device was on.

The device is self-starting, that is to say the shaft 55 is in engagement with the flap 71 when in off condition, gravity holding the shaft against the fiap so that as the motor is energized, engagement occurs.

It can therefore be seen that I have provided an economical yet efiicient oscillator and one which is susceptible of a wide variety of uses.

What I claim is:

1. A mechanical oscillator comprising a housing, an axle mounted on said housing, a disc rotatably mounted coaxially on said axle, a motor mounted adjacent the margin of said disc, said motor including a shaft disposed in parallel relation to said axle, said shaft, said motor and said disc being rockable about said axle in opposite angular directions from a vertical median plane through said axle, means on said housing for intermittently engaging the upper and the lower surfaces of said shaft in alternating fashion whereby said shaft, said motor and said disc are reciprocatingly swung about the axis of said axle as the center of rotation, and means for rotating said shaft.

2. The device of claim 1, wherein said shaft rotating means includes a pair of energized electrical conductors disposed substantially coaxially within said axle, said conductors connecting at one end with said motor and at the other end being led interiorly through said axle and exteriorly of said housing to an electrical energy source remote from said housing.

3. The device of claim 1, wherein said intermittent shaft engaging means comprises a track including a pair of spaced parallel walls defining an arcuate channel, the end of said motor shaft being swingable in opposite directions through said channel for at least a portion of the arcuate path of said shaft, and a flexible strip mounted on said housing and extending across said channel from one end of one of said parallel walls to the other end of the other of said parallel walls whereby said end of said motor shaft alternately engages opposite sides of said strip as said shaft moves in alternating directions through said channel.

4. The device of claim 3, further characterized by means on said disc for changing the period of oscillation of said disc.

5. The device of claim 4, wherein said period changing means includes a tension spring mounted at one end on one of said parallel walls and at the other end on said disc, and means for changing the tension on said spring to a predetermined amount.

6. A mechanical oscillator comprising a housing, an electric motor oscillatably mounted on said housing, said motor including an elongated motor shaft, and reactive means mounted on said housing in interfering relation with said shaft for alternately tractively engaging the opposite sides of said shaft during rotation thereof, whereby said shaft alternately traverses said reactive means in opposite directions and oscillates said motor.

Roth Dec. 2, 1924 Anderson Nov. 6, 1951 

